U.S. patent number 4,614,413 [Application Number 06/697,923] was granted by the patent office on 1986-09-30 for contact lens.
Invention is credited to George A. Obssuth.
United States Patent |
4,614,413 |
Obssuth |
September 30, 1986 |
Contact lens
Abstract
A contact lens is provided having a substantially concavo-convex
lenticular carrier. The carrier has a palpebral anchor portion
which is shaped for seating between the conjunctiva of the lower
eyelid and the inferior sclera of the eyeball, so that the carrier
is held in place with respect to the lower eyelid by the muscles of
the lower eyelid. The carrier also has an optical portion which
projects upwardly from the anchor portion and which has a reading
vision correction area which lies below the pupil of the eye when
the wearer of the lens is looking straight ahead and substantially
covers the pupil when the eye is moved to a reading position. The
junction between the anchor portion and the optical portion extends
substantially along the margin of the lower eyelid. The optical
portion may consist solely of a reading vision correction area, so
that the lens acts as a "half eye" lens, or may also include one or
more distance vision correction areas, so that the lens acts as a
true bifocal or trifocal lens.
Inventors: |
Obssuth; George A. (Washington
Township, Warren County, NJ) |
Family
ID: |
24803138 |
Appl.
No.: |
06/697,923 |
Filed: |
February 5, 1985 |
Current U.S.
Class: |
351/159.02 |
Current CPC
Class: |
G02C
7/04 (20130101); G02C 7/045 (20130101); G02C
7/048 (20130101); G02C 7/041 (20130101) |
Current International
Class: |
G02C
7/04 (20060101); G02C 007/04 () |
Field of
Search: |
;351/16H,16R,161,162 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Corbin; John K.
Assistant Examiner: Sugarman; Scott J.
Attorney, Agent or Firm: Quast; W. Patrick
Claims
What is claimed is:
1. A contact lens comprising a substantially concavo-convex
lenticular carrier having
a palpebral anchor portion shaped for seating between the
conjunctiva of the lower eyelid and the inferior sclera of the
eyeball, and
an optical portion projecting upwardly from said anchor portion,
said optical portion and said anchor portion being so proportioned
that the junction between said portions extends substantially along
the margin of the lower eyelid and the lens is held in place with
respect to the lower eyelid by the muscles of the lower eyelid,
said anchor portion of said lens has a laterally-extending
depression formed therein on the convex side thereof, said
depression being proportional to receive the muscle of Riolan of
the lower eyelid therein.
2. A contact lens as claimed in claim 1 wherein said optical
portion of said lens has a reading vision correction area which
lies below the pupil of the eye when the wearer of the lens is
looking straight ahead and substantially covers the pupil when the
eye is rotated to a reading position.
3. A contact lens as claimed in claim 2 wherein said
laterally-extending depression is a groove located just below said
junction of said lens portions.
4. A contact lens as claimed in claim 3 wherein said anchor portion
of said lens has
an anteriorly-projecting bulge on the convex side thereof extending
along the lower edge thereof for seating in the conjunctival
cul-de-sac of the lower eyelid, and
a laterally-extending band-shaped section on the convex side
thereof joining said groove and said bulge, said band-shaped
section being shaped to receive the tarsal plate of the lower
eyelid, so that the lens is held in place with respect to the lower
eyelid by the muscle of Riolan and the palpebral orbicularis
muscle.
5. A contact lens as claimed in claim 4 wherein
said reading vision correction area of said optical portion of the
lens extends over substantially the entire optical portion, and
the surface area of said optical portion is much smaller than the
surface area of said anchor portion of the lens.
6. A contact lens as claimed in claim 5 wherein an
anteriorly-extending taper is provided on the concave side of said
optical portion of the lens along the upper edge thereof to prevent
irritation of the eye.
7. A contact lens as claimed in claim 2 wherein
the convex surfaces of said optical and anchor portions of the lens
have different radii of curvature and
said laterally-extending depression is formed by the difference in
said radii of curvature, so that said depression extends
substantially along said junction of said lens portions.
8. A contact lens as claimed in claim 7 wherein said anchor portion
of the lens has a vertical cross-section shaped substantially as an
inverted tear drop with the apex of the tear drop located at said
lower edge of said anchor portion.
9. A contact lens as claimed in claim 7 wherein
said lenticular carrier has a vertical cross-section through said
optical and anchor portions shaped substantially as an elongated
tear drop with the apex of the tear drop located at the upper edge
of said optical portion and
the convex surface of said carrier is bifurcated by said
laterally-extending depression.
10. A contact lens as claimed in claim 2 further comprising
a layer of biological adhesive on the convex surface of said anchor
portion of the lens for securing said anchor portion to the
conjunctiva of the lower eyelid to provide additional positional
stability for the lens with respect to the lower eyelid.
11. A contact lens as claimed in claim 3 wherein said anchor
portion of the lens has a vertical cross-section shaped
substantially as a tear drop with the apex of the tear drop located
at said groove.
12. A contact lens as claimed in claim 2 wherein said anchor
portion has vertical cross-sections at the ends thereof which are
thicker than the vertical cross-section at the middle thereof, so
that additional positional stability is provided for the lens with
respect to the lower eyelid.
13. A contact lens as claimed in claim 2 wherein said anchor
portion has
one end thereof which is longer than the other end thereof, and
a lower edge thereof which is skewed with respect to the
horizontal, so that said anchor portion has an overall shape which
is substantially that of a truncated triangle.
14. A contact lens as claimed in claim 2 wherein said anchor
portion has a substantially rectangular overall shape to facilitate
fabrication of the lens.
15. A contact lens as claimed in claim 2 wherein said optical
portion of the lens has a distance vision correction area which
substantially covers the pupil of the eye when the wearer of the
lens is looking straight ahead and lies above the pupil when the
eye is rotated to a reading position.
16. A contact lens as claimed in claim 15 wherein said reading
vision correction area of said optical portion of the lens is
substantially semicircular in shape.
17. A contact lens as claimed in claim 15 wherein said reading
vision correction area of said optical portion of the lens is a
segmental band-shaped area on said optical portion and separates
said distance vision correction area of said optical portion from
said anchor portion.
18. A contact lens as claimed in claim 15 wherein said reading
vision correction area of said optical portion of the lens is
substantially crescent-shaped and separates said distance vision
correction area of said optical portion from said anchor
portion.
19. A contact lens comprising
a substantially concavo-convex lenticular carrier having
a laterally-extending depression on the convex side thereof, said
depression being of a size and shape to receive the muscle of
Riolan of the lower eyelid therein,
an optical portion located on one side of said laterally-extending
depression, said optical portion having a reading vision correction
area of such size and shape as to lie below the pupil of the eye
when the wearer of the lens is looking straight ahead and to
substantially cover the pupil when the eye is rotated to a reading
position, and
a palpebral anchor portion depending from said optical portion,
said anchor portion being of such size and shape as to be seated
between the conjunctiva of the lower eyelid and the inferior sclera
of the eyeball.
20. A contact lens as claimed in claim 19 wherein said optical
portion of the lens also has at least one distance vision
correction area of such size and shape as to lie above the pupil of
the eye when the eye is in a reading position and to substantially
cover the pupil when the eye is rotated to a non-reading
position.
21. A contact lens as claimed in claim 19 wherein said reading
vision correction area of the optical portion of the lens covers
the entire area of said optical portion.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to optical lenses for correcting vision
defects and more particularly to an "anchored" contact lens for
correction of presbyopia and other vision defects.
2. Description of the Prior Art
Prior art attempts to provide contact lenses for the correction of
presbyopia have not been particularly successful. In presbyopic
patients, the lens providing the "reading" or near vision
correction must have positional stability relative to the lower
eyelid, so that it will cover the pupil of the eye only when the
eyeball is rotated downwardly to assume a reading position but will
not cover the pupil when the eye assumes a straight ahead or
distance vision position for which either no correction or only a
distance correction is required.
The older type of contact lens, the so-called "scleral lens",
provided a high degree of positional stability because it was
supported and positioned by the scleral portion of the eyeball and
was permitted little rotational or translational movement relative
to the eye socket and lower eyelid. However, the inherent design of
this lens presented many clinical difficulties during the fitting
and wearing of the lens which eventually led to the development of
the so-called "corneal lens" which essentially "floated" on the
cornea of the eyeball. Although the corneal lens overcame many of
the clinical problems associated with the scleral lens, it was not
amenable to providing reading correction for presbyopic patients
because of its floating or movable position on the cornea of the
eye.
One attempt to provide reading or near vision correction in corneal
lenses involved the use of a substantially circular lens in which
the reading correction was provided by an annular portion which was
concentrically disposed about a centrally located distance vision
correction portion. This type of lens provided reading correction
when the eyeball was rotated to a reading position in which the
pupil was covered by the annular reading correction portion of the
lens and permitted distance correction when the eyeball was rotated
to a straight ahead position so that the central distance vision
correction portion only covered the pupil. This arrangement was
subject to many difficulties, however, because the lens was easily
moved out of position on the cornea during the normal blinking
action of the upper eyelid. The resulting translational or up and
down movement of the lens obviously did not permit the positional
stability required for satisfactory operation of the lens.
Furthermore, the variously sized optic zones of these lenses
produced "ghost" images, blurry vision and other defects.
Another prior art attempt to deal with presbyopia by means of
corneal lenses involved the use of segmented lenses in which a
distance vision correction portion or a non-vision correcting
portion was arranged to cover the pupil with the eye in a straight
ahead position. This lens had a reading vision correction portion
which depended from the distance vision portion and which covered
the pupil when the eye was rotated to a reading position. In this
type of lens, problems were caused by both rotational and
translational movements of the lens because of the segmental shape
of the lens which required exact positional alignment for correct
operation. In order to prevent rotation and translation of the lens
relative to the cornea, this type of lens was provided with an
outwardly or anteriorly projecting flange which engaged the margin
of the lower eyelid to limit rotational movement and provide some
degree of stability during blinking or other translational
movements. The lens, however, still floated on the cornea and was
not positionally stable. Other arrangements for preventing
rotational movement of these lenses involved the use of a ballasted
or weighted lens in which the heaviest and/or largest portion of
the lens was disposed inferiorly of the distance correction portion
so that the force of gravity tended to center the lens and prevent
rotation. Unfortunately, all of these arrangements did not provide
a satisfactory solution to the problem because of the wide range of
lens movements which were still possible.
Still another attempt to provide presbyopic correction involved the
use of a small non-contact lens having a reading correction which
was cemented to the margin of the lower eyelid. This lens projected
up from the lower eyelid margin and was spaced a distance from the
eyeball so that when the eye was closed, the margin of the upper
eyelid could pass between the lens and the eyeball to thereby
permit the eye to be closed with the lens in position. Obviously,
this type of lens was not a contact lens and provided some
inconvenience to the wearer because of the necessity of adhesively
mounting it on the margin of the lower eyelid.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a contact lens for the
correction of presbyopia and other vision disorders which makes use
of the normal anatomical contour of the inferior eye socket to hold
the lens in place.
It is a further object of this invention to provide a contact lens
for the correction of presbyopia and other vision disorders having
a unique anchor portion which is held firmly in the conjunctival
sac of the lower eyelid by the muscles of the lower eyelid, so that
unwanted movements of the lens are prevented.
It is a still further object of this invention to provide a contact
lens of the half-eye type for reading correction which produces no
ghosts, blurry vision or other vision defects and which is not
subject to malfunctions caused by blinking or other eye
movements.
It is an additional object of this invention to provide a contact
lens for reading correction which is easily fitted on the patient
and which may be stocked by the fitter in a limited range of
prescriptions to thereby minimize the inventory of lenses which the
fitter must carry.
It is another object of this invention to provide a contact lens
for the correction of presbyopia and other vision disorders which
is easy and relatively inexpensive to manufacture and which readily
lends itself to fabrication by molding techniques.
It is an additional object of this invention to provide a contact
lens for the correction of presbyopia and other vision disorders
which is easily installed by the wearer of the lens and which is
not subject to accidental dislodgement by normal eye movements.
Briefly, the contact lens of the invention comprises a
substantially concavo-convex lenticular carrier having a palpebral
anchor portion shaped for seating between the conjunctiva of the
lower eyelid and the inferior sclera of the eyeball and an optical
portion projecting upwardly from the anchor portion. The optical
portion and the anchor portion are so proportioned that the
junction between these portions extends substantially along the
margin of the lower eyelid and the lens is held in place with
respect to the lower eyelid by the muscles of the lower eyelid. The
optical portion has a reading vision correction area which lies
below the pupil of the eye when the wearer of the lens is looking
straight ahead and substantially covers the pupil when the eye is
rotated to a reading position. The anchor portion of the lens has a
laterally-extending depression formed therein on the convex side
thereof which is proportioned to receive the muscle of Riolan of
the lower eyelid therein. In a preferred embodiment of the
invention, the laterally-extending depression is a groove located
just below the junction of the lens portions and the anchor portion
has an anteriorly-projecting bulge on the convex side thereof
extending along the lower edge thereof for seating in the
conjunctival cul-de-sac of the lower eyelid and a
laterally-extending band-shaped section on the convex side thereof
joining the groove and the bulge. The band-shaped section is shaped
to receive the tarsal plate of the lower eyelid, so that the lens
is held in place with respect to the lower eyelid by both the
muscle of Riolan and the palpebral orbicularis muscle.
When the reading vision correction area of the optical portion
extends over substantially the entire optical portion, the lens
provides only reading vision correction and functions as a "half
eye" lens. If desired, however, the optical portion of the lens may
also include one or more distance vision correction areas in
addition to the reading vision correction area.
The nature of the invention and other objects and additional
advantages thereof will be more readily understood by those skilled
in the art after consideration of the following detailed
description taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a front view of the human eye showing a contact lens
constructed in accordance with the teachings of the present
invention seated between the conjunctiva of the lower eyelid and
the inferior sclera of the eyeball;
FIG. 2 is a perspective view of a preferred embodiment of the
contact lens of FIG. 1;
FIG. 3 is a top plan view of the lens of FIG. 2;
FIG. 4 is a full sectional view of the lens of FIG. 2 taken along
the line 4--4 thereof;
FIG. 5 is a full sectional view of the lens of FIG. 2 taken along
the line 5--5 thereof;
FIG. 6 is a vertical sectional view of an eye socket showing the
contact lens of FIG. 2 seated in place;
FIG. 7 is a perspective view of a contact lens constructed in
accordance with the present invention having an anchor portion with
a differently shaped cross-section than the lens of FIGS. 1-6;
FIG. 8 is a full sectional view of the lens of FIG. 7 taken along
the line 8--8 thereof;
FIG. 9 is a vertical sectional view of an eye socket showing the
lens of FIG. 7 seated in place therein;
FIG. 10 is a vertical sectional view of an eye socket with the lens
of FIG. 7 seated therein and with a biological adhesive applied to
provide additional positional stability;
FIG. 11 is a perspective view of a contact lens constructed in
accordance with the present invention having an anchor portion with
a muscle receiving groove similar to the lens of FIGS. 1-6 but with
a tear drop shaped vertical cross-section;
FIG. 12 is a full sectional view of the contact lens of FIG. 11
taken along the line 12--12 thereof;
FIG. 13 is a perspective view of a contact lens constructed in
accordance with the teachings of the invention wherein the
lenticular carrier has a vertical cross-section through the optical
and anchor portions shaped substantially as an elongated tear
drop;
FIG. 14 is a full sectional view of the lens of FIG. 13 taken along
the line 14--14 thereof;
FIGS. 15 and 16 are perspective views of contact lenses constructed
in accordance with the present invention having anchor portions
with different overall shapes;
FIG. 17 is a perspective view of a contact lens constructed in
accordance with the present invention which is especially suited
for use by wearers having flaccid muscles in the lower eyelid;
FIG. 18 is a top plan view of the contact lens of FIG. 17;
FIG. 19 is a perspective view of a contact lens constructed in
accordance with the present invention which provides both reading
and distance vision correction areas in the optical portion
thereof; and
FIGS. 20 and 21 are perspective views of contact lenses which are
similar to the lens of FIG. 19 but which have differently shaped
reading and distance vision correction areas in the optical
portions thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
Referring now to FIG. 1 of the drawings, a contact lens constructed
in accordance with the teachings of the present invention is shown
in place in the eye of a wearer of the lens. The contact lens
comprises a substantially concavo-convex lenticular carrier,
indicated generally as 30, which has a vision-correcting or optical
portion 31 and a non-vision correcting palpebral anchor portion 32.
The eyeball has a scleral portion, indicated generally as 33, and a
corneal portion, indicated generally as 34. The junction between
the scleral and corneal portions of the eye is the substantially
circular limbus, indicated generally as 35. The palpebral anchor
portion 32 of the lens has a size and shape which permit it to be
seated between the conjunctiva of the lower eyelid and the inferior
or lower portion of the sclera of the eye. The optical portion 31
of the lens projects upwardly from the anchor portion and is of
sufficient size to permit the pupil 36 of the eye to be
substantially covered by the optical portion when the eyeball is
rotated downwardly to a reading position. The optical portion and
the anchor portion of the lens are so proportioned that the
junction 37 between these portions extends substantially along the
margin of the lower eyelid and the lens is held in place with
respect to the lower eyelid by the muscles of the lower eyelid.
When the eye is looking straight ahead, as shown in FIG. 1, the
inferior or lowermost point of the limbus 35 is located at the
margin 38 of the lower eyelid and hence at the junction 37 between
the optical and anchor portions of the lens. The lens is so
proportioned that the uppermost point or top of the optical portion
31 lies just below the pupil 36 of the eye with the eye in a
straight ahead or distance vision position.
When the eye is rotated downwardly into a normal reading position,
the cornea 34 rotates downwardly approximately 51/2 millimeters
while the margin 38 of the lower eyelid moves down only about 21/2
millimeters. Accordingly, for optical correction of presbyopia, the
reading portion of a corrective lens must sit just below the
pupillary margin when the eye is in a straight ahead position and
must remain still relative to the lower lid when the eye is rotated
downwardly to the reading position. Since the diameter of an
average pupil with a normal level of illumination is approximately
3 to 31/2 millimeters and since the average movement of the cornea
below the margin of the lower eyelid is approximately 3 millimeters
with the eye in a reading position, it is apparent that the
operation of a reading contact lens will only be satisfactory if
the lens is held completely still with respect to the lower eyelid.
In the lens of the invention, the anchor portion 30 lies below the
margin 38 of the lower eyelid and is held in place with respect to
the lower eyelid, as will be explained hereinafter, so that the
lens moves downwardly with the lower eyelid when the eye is rotated
to a reading position. This permits the pupil 36 of the eye to be
substantially covered by the optical portion 31 of the lens. When
the eye is looking straight ahead, the optical portion 31 of the
lens lies just below the margin of the pupil 36 so that it will not
interfere with the distance vision of the wearer of the lens.
A preferred configuration of the anchor portion of the contact lens
of the invention is shown in detail in FIGS. 2 through 6 of the
drawings. As seen therein, the lenticular carrier 30 has a
generally concave posterior surface, indicated generally as 39,
which substantially conforms to the shape of the anterior surface
40 of the eyeball. As seen in FIGS. 4 and 6, the surface 39 of the
lens has a part 41 which substantially conforms to the radius of
the corneal portion 34 of the eye and a part 42 which substantially
conforms to the radius of the scleral portion 33 of the eye. The
anterior or convex surface, indicated generally as 43, of the lens
has a lower part 44 which is shaped to conform to the anatomical
contours of the posterior surface of the lower eyelid 45. The lower
eyelid 45 has an inwardly or posteriorly-projecting portion 46
which is produced by the laterally-extending muscle of Riolan which
lies just below the upper margin 38 of the lower eyelid. In order
to accomodate this portion, the convex surface of the anchor
portion of the lens is provided with a laterally-extending
depression 48. The depression is in the form of a groove which is
located just below the junction 37 of the optical and anchor
portions and which is proportioned to receive the muscle of Riolan
therein. An anteriorly-projecting bulge 49 on the convex side of
the anchor portion extends along the lower edge thereof for seating
in the conjunctival cul-de-sac 50 of the lower eyelid. The groove
48 and the projecting bulge 49 on the convex side of the anchor
portion are joined by a relatively smooth, laterally-extending
band-shaped section 44A which is shaped to receive the tarsal plate
51 of the lower eyelid, so that the lens is held in place with
respect to the lower eyelid by the palpebral orbicularis muscle
which is located in the lower eyelid between the muscle of Riolan
46 and the conjunctival cul-de-sac 50. The blinking of the human
eye is caused by a contraction of the orbicularis muscle. Since the
palpebral orbicularis muscle is located anteriorly of the tarsal
plate in the lower eyelid, the contact lens is anchored in place
with respect to the lower eyelid by both the muscle of Riolan and
the palpebral orbicularis muscle.
The foregoing configuration of the anchor portion of the carrier
permits it to be held firmly in place with respect to the lower
eyelid when the eyeball is rotated in any direction. The lens is
forced against the eyeball by the palpebral orbicularis muscle and
the muscle of Riolan. The groove 48 and the bulge 49 on the anchor
portion of the lens prevent both upward and downward translatory
movement of the lens as well as rotational movement. An
anteriorly-extending taper or bevel 52 is provided on the concave
side of the optical portion 31 of the lens along the upper edge
thereof to prevent scratching or irritation of the eyeball by the
upper edge of the lens. In this embodiment of the invention, a
reading vision correction area extends over the entire optical
portion 31 so that the lens functions in the manner of "half eye"
eyeglasses to provide reading vision correction only. Approximate
dimensions of the contact lens shown in FIGS. 2 through 6 of the
drawings are shown in FIGS. 2 and 4. It will be understood,
however, that a range of dimensions will be required to accomodate
the range of wearer eye dimensions encountered in practice.
A contact lens constructed in accordance with the present invention
and having a somewhat different anchor portion is shown in FIGS. 7
through 9 of the drawings. As seen therein, this lens, indicated
generally as 60, is provided with an optical portion 61 and a
palpebral anchor portion 62. In this configuration, as seen in FIG.
8, the thickness of the anchor portion 62 of the lens increases
sharply from the junction line 63 between the optical and anchor
portions until it reaches a maximum at a point 64 which is somewhat
below the muscle of Riolan. The thickness then continually
decreases until it reaches the inferior or lower edge 65 of the
lens. The convex surfaces of the optical and anchor portions of the
lens have different radii of curvature and the difference in the
radii of curvature forms a laterally-extending depression which
extends substantially along the junction 63 of the lens portions.
The depression thus formed accomodates the muscle of Riolan and the
margin 38 of the lower eyelid as seen in FIG. 9. In this
configuration, the anteriorly-projecting bulge 49 shown in the
embodiment of FIGS. 2 through 6 of the drawings is eliminated as is
the sharply defined groove 48. Accordingly, the anchor portion 62
has a vertical cross-section shaped substantially as an inverted
tear drop with the apex of the tear drop located at the lower edge
65 of the anchor portion. Since the muscle of Riolan and the margin
of the lower eyelid are above the point 64 of greatest thickness,
the lens is still well anchored in place and translational and
rotational movement are prevented.
Although the anchor portions of the contact lenses hereinbefore
described provide excellent anchoring and positional stability for
the lenses for the vast majority of wearers, the contours of the
conjunctival sac of the lower eyelid of some wearers may require
additional measures such as the use of a biological adhesive
between the conjunctiva of the lower eyelid and the anterior or
convex surface of the anchor portion of the contact lens. As seen
in FIG. 10, a layer 70 of a suitable biological adhesive is applied
between the conjunctival surface 71 of the lower eyelid 72 and the
anterior surface 73 of the anchor portion 74 of the lens. For
purposes of illustration, the thickness of the layer 70 of adhesive
has been greatly exaggerated. Biological adhesives suitable for
this purpose are well known in the art and are often used for other
purposes, such as the affixation of false eyelashes, for
example.
FIGS. 11 and 12 of the drawings show a contact lens, indicated
generally as 80, having a still different configuration of the
anchor portion of the lens. As seen therein, the lens has an anchor
portion 81 and an optical portion 82. The anchor portion 81 has a
laterally-extending groove 83 which is located just below the
junction of the lens portions in the same manner as the groove 48
in the lens of FIGS. 1-6. This groove also accomodates the muscle
of Riolan. The anchor portion 81, however, gradually increases in
thickness from the groove 83 towards its inferior or lower edge 84
which is suitably rounded to fit easily into the conjunctival
cul-de-sac of the lower eye, so that the anchor portion has a
vertical cross-section shaped substantially as a tear drop with the
apex of the tear drop located at the groove 83. This anchor portion
configuration also eliminates the anteriorly-projecting bulge 49 of
the embodiment of FIGS. 2-6 of the drawings and still provides
sufficient anchoring and positional stability for the lens. The
optical portion 82 of this lens is also provided with a bevelled or
tapered portion 85 on the posterior or concave surface 86 of the
lens which extends along the upper edge 87 to prevent eye
irritation. The bevelling is accomplished by the use of different
radii of curvature for the bevelled portion 85 and the remainder of
the posterior surface 86 of the lens.
In FIGS. 13 and 14 of the drawings, a variation in the overall
cross-section of the contact lens is shown. As seen therein, the
lens, indicated generally as 90, has a vertical cross-section
through the optical and anchor portions which is shaped
substantially as an elongated teardrop with the apex of the
teardrop located at the upper edge of the optical portion. The
optical portion 91 and the anchor portion 92 are separated by only
a small or shallow laterally-extending depression 93 which is
formed by the difference in radii of curvature of the convex
surfaces of the lens. The laterally-extending depression 93 which
is similar to the depression 63 in the lens of FIGS. 7-9,
substantially bifurcates the convex surface of the lenticular
carrier. Although this configuration of lens does not provide the
same high degree of positional stability as the previously
described anchor configurations, it may be useful for some lens
wearers, particularly when used with a biological adhesive such as
shown in FIG. 10 of the drawings.
As thus far described, it is apparent that the cross-section of the
anchor portion of the contact lens of the invention may comprise
several different configurations. However, as seen in FIGS. 15 and
16, the overall shape of the anchor portion and the overall shape
of the optical portion of the lens may also be varied for
particular purposes. For example, the lens, indicated generally as
95, shown in FIG. 15 has an optical portion 96 which has a
relatively flat or straight upper edge 97. Furthermore, the anchor
portion 98 of this lens has a substantially rectangular overall
shape which readily lends itself to simple fabrication techniques.
In FIG. 16, the lens, indicated generally as 100, has an optical
portion 101 with a substantially semicircular upper edge 102. The
anchor portion 103 of this lens has one end 100A thereof which is
longer than the other end 100B thereof and a lower edge 104 which
is skewed with respect to the horizontal, so that the anchor
portion has an overall shape which is substantially that of a
truncated triangle. This provides additional positional stability
and thereby prevents the lens fron rotating up and out from under
the lower eyelid. A lens for the other eye of the wearer would be a
mirror image of this lens.
The lens shown in FIGS. 17 and 18 of the drawings provides
additional positional stability to facilitate use by elderly
wearers having relatively flaccid muscles of Riolan and orbicularis
muscles. This lens, indicated generally as 110, has an anchor
portion 111 and an optical portion 112. The anchor portion 111 has
vertical cross-sections at the ends 113 thereof which are thicker
than the vertical cross-section at the middle thereof, so that
additional positional stability is provided which prevents the lens
from rotating with respect to the lower eyelid.
It is believed apparent from the foregoing description that
different combinations of the aforedescribed optical and anchor
portions may be employed to suit a particular wearer or to provide
a desired manufacturing objective. It is also apparent that each of
the foregoing lenses provides a reading correction contact lens
which provides excellent positional stability and which does not
interfere with the normal distance vision of the wearer.
Furthermore, the aforedescribed reading contact lens of the
invention does not suffer from the previously described problems
encountered by prior art lenses such as ghosts, blurry vision and
unwanted rotational and translational movements. Since the optical
reading portion of the lens is supported by a non-vision correcting
anchor portion which is disposed between the lower eyelid and the
eye, a light-transmitting anchor portion need not be employed as
required in some of the described prior art lenses. A practicioner
who fits these lenses need only carry a limited range of reading
correction prescriptions since the anchor portion will fit most of
the patients encountered in normal practice. This greatly
facilitates patient treatment because the practicioner need carry
only a small inventory of lenses to provide a correct prescription
for the patient which accordingly permits the lens to be fitted on
a first office visit. Additionally, manufacturing costs are also
reduced because of the reduction in range of prescriptions that
must be made by the manufacturer. The contact lens of the invention
may be fabricated from any of the soft, pliable, transparent
materials, such as a hemaplastic material, for example, which are
in use today for the floating or corneal type of contact lens.
Similarly, if the patient can tolerate a harder material, the lens
of the invention may be made of the older, harder and less pliable
materials.
Although the contact lens of the invention has been developed
primarily for correction of presbyopia in patients who do not
require a distance vision correction, it is possible to incorporate
both presbyopic and myopic or hyperopic correction in a single
contact lens constructed in accordance with the invention. As seen
in FIG. 19 of the drawings, a contact lens, indicated generally as
120, is provided with an anchor portion 121 which may be
constructed as hereinbefore described. The optical portion 122 of
the lens, however, has not only a reading vision correction area
122A which may be shaped and proportioned in the same manner as the
optical portions of the hereinbefore described lenses, but also a
distance vision correction area 122B. The distance vision
correction area is so sized and shaped as to substantially cover
the pupil of the eye when the wearer of the lens is looking
straight ahead and to lie above the pupil when the eye is rotated
to a reading position, so that distance vision correction is
provided for all normal positions of the eye except the downward or
reading position. The lenticular carrier is provided with the
concavo-convex configuration utilized in the previously described
embodiments of the invention.
Contact lenses having the same reading and distance vision
corrections as the lens of FIG. 19 but with differently shaped
optical areas are shown in FIGS. 20 and 21. The lens, indicated
generally as 130, shown in FIG. 20 has an optical portion 131
having a reading vision correction area 131A which is a segmental
band-shaped area separating the distance vision correction area
131B and the anchor portion 132 of the lens. In FIG. 21, the lens,
indicated generally as 140, has an optical portion 141 having a
reading vision correction area 141A and a distance vision
correction area 141B thereon. The reading correction area 141A of
the optical portion 141 is substantially crescent-shaped and
separates the distance vision area 141B from the anchor portion 142
of the lens. This arrangement will provide reading or near vision
correction over a somewhat wider visual field than the lens
configurations shown in FIGS. 19 and 20 and may be suitable for
tasks requiring the wider area of reading correction. The anchor
portion 142 of the lens 140 may be shaped and sized as hereinbefore
described. It is obvious that the optical portions of any of the
lenses shown in FIGS. 19, 20 and 21 may include not only reading
vision correction and distance vision correction but also
intermediate vision correction, so that the lens acts as a trifocal
lens.
It is believed apparent that many changes could be made in the
construction and described uses of the foregoing contact lens and
many seemingly different embodiments of the invention could be
constructed without departing from the scope thereof. Accordingly,
it is intended that all matter contained in the above description
or shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
* * * * *